package com.huaxia.day18;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class Calculator {
    public static void main(String[] args) {
        EventQueue.invokeLater(() -> {
            CalculatorFrame frame = new CalculatorFrame();
            frame.setTitle("计算器");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setVisible(true);
        });
    }
}

class CalculatorFrame extends JFrame{
    public CalculatorFrame() {
        add(new CalculatorPanel());
        pack();
    }

}

class CalculatorPanel extends JPanel{
    private JPanel panel;
    private JTextField display;
    private double result;
    private String lastcommand;
    private boolean start=true;
    public CalculatorPanel() {
        setLayout(new BorderLayout());
        display=new JTextField();
        display.setHorizontalAlignment(JTextField.RIGHT);
        result=0;
        display.setText(""+result);
        add(display,BorderLayout.NORTH);
        ActionListener insert=new InsertAction();
        ActionListener command=new CommandAction();
        panel=new JPanel();
        panel.setLayout(new GridLayout(4,4));//网格布局
        addButton("7",insert);
        addButton("8",insert);
        addButton("9",insert);
        addButton("/",command);
        addButton("4",insert);
        addButton("5",insert);
        addButton("6",insert);
        addButton("*",command);
        addButton("1",insert);
        addButton("2",insert);
        addButton("3",insert);
        addButton("+",command);
        addButton("0",insert);
        addButton(".",insert);
        addButton("=",command);
        addButton("+",command);
        add(panel, BorderLayout.CENTER);
    }

    private void addButton(String s, ActionListener listener) {
        JButton button=new JButton(s);
        button.addActionListener(listener);
        panel.add(button);
    }

    private class InsertAction implements ActionListener{
        public void actionPerformed(ActionEvent event) {
            String input=event.getActionCommand();
            if(start){
                display.setText("");
                start=false;
            }
            display.setText(display.getText()+input);
        }
    }
    private class CommandAction implements ActionListener{
        public void actionPerformed(ActionEvent event) {
            String command=event.getActionCommand();
            if(command.equals("=")){
                if(lastcommand.equals("+")) result+=Double.parseDouble(display.getText());
                if(lastcommand.equals("-")) result-=Double.parseDouble(display.getText());
                if(lastcommand.equals("*")) result*=Double.parseDouble(display.getText());
                if(lastcommand.equals("/")) result/=Double.parseDouble(display.getText());
                display.setText(""+result);
                start=true;
            }else{
                result=Double.parseDouble(display.getText());
                lastcommand=command;
                start=true;
            }
        }
    }

}
